This service enables you to identify the receiving party, i.e. the subscriber loop that is being called. For example, when forwarding, the number to which incoming calls have been forwarded will be displayed.
While establishing a connection, the network will submit the receiving party's number to a calling party that has enabled the COLP service, regardless of the ability of the caller's terminal to process such information.
If the receiving party has submitted its number, the network always checks its validity. This check is performed by the exchange to which the receiving party is connected. In the case of calling a private branch exchange (PBX), the network checks whether a given number is in the range of the PBX's numbering. In the case of the ISDN MSN add-on service, the network on the receiving party's side checks whether the number is one of the numbers that were assigned to the given subscriber's access.
If the receiving terminal does not provide a number or if the check performed by the public network was successful, the exchange on the calling party's side submits the standard national number of the receiving party, marked as "provided by network".